KVM: trivial documentation cleanups

Add missing entries to the index and ensure the entries are in
alphabetical order. Also amd-memory-encryption.rst is an .rst
not a .txt.
Signed-off-by: NAndrew Jones <drjones@redhat.com>
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>

Documentation/virtual/kvm/00-INDEX

 00-INDEX
 	- this file.
+amd-memory-encryption.rst
+	- notes on AMD Secure Encrypted Virtualization feature and SEV firmware
+	  command description
 api.txt
 	- KVM userspace API.
+arm
+	- internal ABI between the kernel and HYP (for arm/arm64)
 cpuid.txt
 	- KVM-specific cpuid leaves (x86).
 devices/
@@ -26,6 +31,5 @@ s390-diag.txt
 	- Diagnose hypercall description (for IBM S/390)
 timekeeping.txt
 	- timekeeping virtualization for x86-based architectures.
-amd-memory-encryption.txt
-	- notes on AMD Secure Encrypted Virtualization feature and SEV firmware
-	  command description
+vcpu-requests.rst
+	- internal VCPU request API

Documentation/virtual/kvm/api.txt

@@ -3480,7 +3480,7 @@ encrypted VMs.
 
 Currently, this ioctl is used for issuing Secure Encrypted Virtualization
 (SEV) commands on AMD Processors. The SEV commands are defined in
-Documentation/virtual/kvm/amd-memory-encryption.txt.
+Documentation/virtual/kvm/amd-memory-encryption.rst.
 
 4.111 KVM_MEMORY_ENCRYPT_REG_REGION